Factors affecting the species composition of arable field boundary vegetation.
To determine the most important factors related to the species composition of arable field boundaries, the vegetation composition of 105 1-m wide herbaceous boundaries in the central and eastern Netherlands was surveyed in June and July 1995. Biomass samples of the boundary were taken at 0-33, 34-66 and 67-100 cm from the adjacent arable field. Farmers were interviewed with respect to boundary management and land use on the adjacent arable field. The nitrogen and phosphorus inputs to the crop were closely correlated to another environmental variable, crop rotation. Crop rotations dominated by maize cultivation received significantly higher nutrient inputs than the other rotations. Nitrogen, phosphorus and crop rotation were strongly correlated with the composition of the boundary vegetation. Species richness of the boundary vegetation was negatively related to nitrogen and phosphorus inputs to the crop, while total boundary biomass was negatively related to nitrogen inputs only. Furthermore, there was a significant relationship between the partitioning of the boundary vegetation between different functional groups and both nitrogen inputs and crop rotation on the adjacent arable field. No significant relationships were found between the vegetation composition and either herbicide use in the boundary or boundary management. This may have been due to the descriptive approach of the study: little variation in boundary management as well as herbicide use in the boundary was observed in the study area. The boundary vegetation was characterized by a peak in biomass production in the zone near the arable field. In this zone the perennial arable weed Elymus repens, as well as annual dicotyledonous species, were significantly more abundant, while perennial dicotyledons and monocotyledons were significantly less abundant compared with the zones further from the arable field. Efforts to protect field boundary vegetation need to focus on a reduction or cessation of fertilizer applications in the outer metre(s) of crops that require high nutrient inputs.